1. Field of the Invention
The present invention relates to a cutting method and a cutter apparatus for cutting a coil conductor to be used, for example, in an armature coil of an engine starter.
2. Description of the Related Art
FIG. 7 schematically shows the construction of a conventional cutter apparatus for coil conductor such as disclosed in Japanese Patent Publication No.62-48471. In this figure, a coil conductor 2 having a circular cross section contained in a bobbin 1 is drawn out from the bobbin 1 by a predetermined amount by means of feed rollers 3 and then is brought to a halt. Insulating film on its periphery is scraped off for a range of length 2L by a helical reamer 4. Thereafter, the coil conductor 2 is severed at the center of the 2L range by a pair of cutting edges 5A, 5B. Thus, as shown in FIG. 8, of the severed coil conductor 2, the insulating film has been scraped off for a length L at each end. Further, the coil conductor 2 drawn out from the bobbin 1 is removed of its warping by straightening roller 6.
The severed coil conductor 2 is formed into a shape for example shown in FIG. 9 and is inserted into a slot 7a of an armature core 7 as shown in FIG. 10. Thereafter, as shown in FIG. 11, the portion of the coil conductor 2 penetrating through the armature core 7 is formed and the portions with the insulating film being scraped off are connected to a commutator 8. In this manner, the armature for an engine starter is assembled.
FIG. 12 schematically illustrates the method of cutting by the apparatus of FIG. 7. A terminal end of the coil conductor 2 is grasped by a catcher 9 so that it may be advanced or pulled away after severing. Cutting edges 5A, 5B are connected to driving shafts 11A, 11B through cutting eccentric cam mechanisms 10A, 10B, respectively. Rotation of the driving shafts 11A, 11B is converted into a linear movement of the cutting edges 5A, 5B by the cutting eccentric cam mechanisms 10A, 10B.
FIG. 13 is an enlarged view showing the state of cutting the coil conductor of FIG. 2. The cutting edges 5A, 5B are moved in the direction perpendicular to the feeding direction of the coil conductor 2 so as to cut the coil conductor 2. Further, the tool angle at each of the cutting edges 5A, 5B is 90.degree.. The reason for this is that both end portions of the coil conductor 2 after the severance are sharpened so that its insertion into the slot 7a of the armature core 7 is smooth.
In the conventional cutting method of the coil conductor 2 as described above, though feeding of the coil conductor 2 comes to a halt at the time of its cutting, since the cutting edges 5A, 5B are moved perpendicularly with respect to the coil conductor 2, the coil conductor 2 located upstream of the cutting edges 5A, 5B is pressed backwards or push-cammed in a direction opposite to its feeding by the tool surfaces of the cutting edges 5A, 5B. At this time, since the "reverse" movement of the coil conductor 2 in the direction opposite to its feeding is restricted by the feed roller 3, the coil conductor 2 is deflected as shown in FIG. 13 to result in a bending of the coil conductor 2 or unstable dimensions of the coil conductor 2 after the severance. Further, a pressing force is exerted on the cutting edges 5A, 58 from the coil conductor 2, causing a premature wear or noise of the cutting edges 5A, 5B.
On the other hand, the coil conductor 2 downstream the cutting edges 5A, 5B, though it is pushed in the direction of its feeding when being cut, causes no problem, since the catcher 9 does not restrict the movement in the feeding direction of the coil conductor 2.